Showing papers on "Biofilm matrix published in 2004"
TL;DR: This work has focused on the influence of biomineralization processes taking place on metallic surfaces and the impact of extracellular enzymes, active within the biofilm matrix, on electrochemical reactions at theBiofilm-metal interface.
817 citations
TL;DR: From the experiments, it is concluded that AST methods enhance cake dewaterability in two ways: they degrade EPS proteins and polysaccharides reducing the EPS water retention properties; and they promote flocculation which reduces the amount of fine flocs.
671 citations
TL;DR: RetS is defined as a pleiotropic regulator of multiple virulence phenotypes that orchestrates genes required for acute infection and genes associated with chronic persistence.
598 citations
TL;DR: Scanning electron microscopy is used to demonstrate that the exopolysaccharide intercellular adhesin (PIA) resides in fibrous strands on the bacterial cell surface, and that lack of PIA production results in complete loss of the extracellular matrix material that has been suggested to mediate immune evasion.
Abstract: The skin commensal and opportunistic pathogen Staphylococcus epidermidis is the leading cause of nosocomial and biofilm-associated infections. Little is known about the mechanisms by which S. epidermidis protects itself against the innate human immune system during colonization and infection. We used scanning electron microscopy to demonstrate that the exopolysaccharide intercellular adhesin (PIA) resides in fibrous strands on the bacterial cell surface, and that lack of PIA production results in complete loss of the extracellular matrix material that has been suggested to mediate immune evasion. Phagocytosis and killing by human polymorphonuclear leucocytes was significantly increased in a mutant strain lacking PIA production compared with the wild-type strain. The mutant strain was also significantly more susceptible to killing by major antibacterial peptides of human skin, cationic human beta-defensin 3 and LL-37, and anionic dermcidin. PIA represents the first defined factor of the staphylococcal biofilm matrix that protects against major components of human innate host defence.
589 citations
TL;DR: Either carbohydrate-rich matrix component appears to be sufficient for mature biofilm formation, and at least one of them is required for matureBiofilm formation in P. aeruginosa strains PA14 and ZK2870.
Abstract: Pseudomonas aeruginosa forms biofilms, which are cellular aggregates encased in an extracellular matrix. Molecular genetics studies of three common autoaggregative phenotypes, namely wrinkled colonies, pellicles, and solid-surface-associated biofilms, led to the identification of two loci, pel and psl, that are involved in the production of carbohydrate-rich components of the biofilm matrix. The pel gene cluster is involved in the production of a glucose-rich matrix material in P. aeruginosa strain PA14 (L. Friedman and R. Kolter, Mol. Microbiol. 51:675-690, 2004). Here we investigate the role of the pel gene cluster in P. aeruginosa strain ZK2870 and identify a second genetic locus, termed psl, involved in the production of a mannose-rich matrix material. The 11 predicted protein products of the psl genes are homologous to proteins involved in carbohydrate processing. P. aeruginosa is thus able to produce two distinct carbohydrate-rich matrix materials. Either carbohydrate-rich matrix component appears to be sufficient for mature biofilm formation, and at least one of them is required for mature biofilm formation in P. aeruginosa strains PA14 and ZK2870.
492 citations
TL;DR: It is discovered that one group of genes, designated psl, are important for biofilm initiation and understanding psl-encoded exopolysaccharide expression and protection in biofilms will provide insight into the pathogenesis of P. aeruginosa in cystic fibrosis and other infections involving biofilmms.
Abstract: Bacteria inhabiting biofilms usually produce one or more polysaccharides that provide a hydrated scaffolding to stabilize and reinforce the structure of the biofilm, mediate cell-cell and cell-surface interactions, and provide protection from biocides and antimicrobial agents. Historically, alginate has been considered the major exopolysaccharide of the Pseudomonas aeruginosa biofilm matrix, with minimal regard to the different functions polysaccharides execute. Recent chemical and genetic studies have demonstrated that alginate is not involved in the initiation of biofilm formation in P. aeruginosa strains PAO1 and PA14. We hypothesized that there is at least one other polysaccharide gene cluster involved in biofilm development. Two separate clusters of genes with homology to exopolysaccharide biosynthetic functions were identified from the annotated PAO1 genome. Reverse genetics was employed to generate mutations in genes from these clusters. We discovered that one group of genes, designated psl, are important for biofilm initiation. A PAO1 strain with a disruption of the first two genes of the psl cluster (PA2231 and PA2232) was severely compromised in biofilm initiation, as confirmed by static microtiter and continuous culture flow cell and tubing biofilm assays. This impaired biofilm phenotype could be complemented with the wild-type psl sequences and was not due to defects in motility or lipopolysaccharide biosynthesis. These results implicate an as yet unknown exopolysaccharide as being required for the formation of the biofilm matrix. Understanding psl-encoded exopolysaccharide expression and protection in biofilms will provide insight into the pathogenesis of P. aeruginosa in cystic fibrosis and other infections involving biofilms.
387 citations
TL;DR: The rat central venous catheter model provides a model for further investigation into the molecular mechanisms of C. albicans biofilm biology and drug resistance and provides a means to study novel drug therapies and device technologies targeted to the control of biofilm-associated infections.
Abstract: Biofilms represent a niche for microorganisms where they are protected from both the host immune system and antimicrobial therapies. Biofilm growth serves as an increasing source of clinical infections. Candida infections are difficult to manage due to their persistent nature and associated drug resistance. Observations made in biofilm research have generally been limited to in vitro models. Using a rat central venous catheter model, we characterized in vivo Candida albicans biofilm development. Time-course quantitative culture demonstrated a progressive increase in the burden of viable cells for the first 24 h of development. Fluorescence and scanning electron microscopy revealed a bilayered architecture. Adjacent to the catheter surface, yeast cells were densely embedded in an extracellular matrix. The layer adjacent to the catheter lumen was less dense. The outermost surface of the biofilm contained both yeast and hyphal forms, and the extracellular material in which they were embedded appeared fibrous. These architectural features were similar in many respects to those described for in vitro models. However, scanning electron microscopy also revealed host cells embedded within the biofilm matrix. Drug susceptibility was determined by using two assays and demonstrated a biofilm-associated drug resistance phenotype. The first assay demonstrated continued growth of cells in the presence of supra-MIC antifungal drug concentrations. The second assay demonstrated reduced susceptibility of biofilm-grown cells following removal from the biofilm structure. Lastly, the model provided sufficient nucleic material for study of differential gene expression associated with in vivo biofilm growth. Two fluconazole efflux pumps, CDR1 and CDR2, were upregulated in the in vivo biofilm-associated cells. Most importantly, the studies described provide a model for further investigation into the molecular mechanisms of C. albicans biofilm biology and drug resistance. In addition, the model provides a means to study novel drug therapies and device technologies targeted to the control of biofilm-associated infections.
366 citations
TL;DR: It is demonstrated that, in the bovine intramammary gland, the presence of Bap may facilitate a biofilm formation connected with the persistence of S. aureus.
Abstract: Staphylococcus aureus is a common cause of intramammary infections, which frequently become chronic, associated with the ability of the bacteria to produce biofilm. Here, we report a relationship between the ability to produce chronic bovine mastitis and biofilm formation. We have classified bovine mastitis S. aureus isolates into three groups based on the presence of particular genetic elements required for biofilm formation: group 1 (ica+ bap+), group 2 (ica+, bap negative), and group 3 (ica negative, bap negative). Overall, animals naturally infected with group 1 and 2 isolates had a lower milk somatic cell count than those infected with isolates of group 3. In addition, Bap-positive isolates were significantly more able to colonize and persist in the bovine mammary gland in vivo and were less susceptible to antibiotic treatments when forming biofilms in vitro. Analysis of the structural bap gene revealed the existence of alternate forms of expression of the Bap protein in S. aureus isolates obtained under field conditions throughout the animal's life. The presence of anti-Bap antibodies in serum samples taken from animals with confirmed S. aureus infections indicated the production of Bap during infection. Furthermore, disruption of the ica operon in a bap-positive strain had no effect on in vitro biofilm formation, a finding which strongly suggested that Bap could compensate for the deficiency of the PIA/PNAG product (a biofilm matrix polysaccharide). Altogether, these results demonstrate that, in the bovine intramammary gland, the presence of Bap may facilitate a biofilm formation connected with the persistence of S. aureus.
365 citations
TL;DR: It is confirmed that PGA functions as a biofilm matrix polysaccharide in phylogenetically diverse bacterial species and suggested that P GA may play a role in intercellular adhesion and cellular detachment and dispersal in A. pleuropneumoniae biofilms.
Abstract: Biofilms are composed of bacterial cells embedded in an extracellular polysaccharide matrix. A major component of the Escherichia coli biofilm matrix is PGA, a linear polymer of N-acetyl-d-glucosamine residues in β(1,6) linkage. PGA mediates intercellular adhesion and attachment of cells to abiotic surfaces. In this report, we present genetic and biochemical evidence that PGA is also a major matrix component of biofilms produced by the human periodontopathogen Actinobacillus actinomycetemcomitans and the porcine respiratory pathogen Actinobacillus pleuropneumoniae. We also show that PGA is a substrate for dispersin B, a biofilm-releasing glycosyl hydrolase produced by A. actinomycetemcomitans, and that an orthologous dispersin B enzyme is produced by A. pleuropneumoniae. We further show that A. actinomycetemcomitans PGA cross-reacts with antiserum raised against polysaccharide intercellular adhesin, a staphylococcal biofilm matrix polysaccharide that is genetically and structurally related to PGA. Our findings confirm that PGA functions as a biofilm matrix polysaccharide in phylogenetically diverse bacterial species and suggest that PGA may play a role in intercellular adhesion and cellular detachment and dispersal in A. actinomycetemcomitans and A. pleuropneumoniae biofilms.
304 citations
TL;DR: The results indicate that most GGDEF proteins of S. typhimurium are functionally related, probably by controlling the levels of the same final product (cyclic di‐GMP), which include among its regulatory targets the cellulose production and biofilm formation of S.
Abstract: Summary
Salmonella enterica serovar Typhimurium is capable of producing cellulose as the main exopolysaccharide compound of the biofilm matrix. It has been shown for Gluconacetobacter xylinum that cellulose biosynthesis is allosterically regulated by bis-(3′,5′) cyclic diguanylic acid, whose synthesis/degradation depends on diguanylate cyclase/phosphodiesterase enzymatic activities. A protein domain, named GGDEF, is present in all diguanylate cyclase/phosphodiesterase enzymes that have been studied to date. In this study, we analysed the molecular mechanisms responsible for the failure of Salmonella typhimurium strain SL1344 to form biofilms under different environmental conditions. Using a complementation assay, we were able to identify two genes, which can restore the biofilm defect of SL1344 when expressed from the plasmid pBR328. Based on the observation that one of the genes, STM1987, contains a GGDEF domain, and the other, mlrA, indirectly controls the expression of another GGDEF protein, AdrA, we proceeded on a mutational analysis of the additional GG[DE]EF motif containing proteins of S. typhimurium. Our results demonstrated that MlrA, and thus AdrA, is required for cellulose production and biofilm formation in LB complex medium whereas STM1987 (GGDEF domain containing protein A, gcpA) is critical for biofilm formation in the nutrient-deficient medium, ATM. Insertional inactivation of the other six members of the GGDEF family (gcpB-G) showed that only deletion of yciR (gcpE) affected cellulose production and biofilm formation. However, when provided on plasmid pBR328, most of the members of the GGDEF family showed a strong dominant phenotype able to bypass the need for AdrA and GcpA respectively. Altogether, these results indicate that most GGDEF proteins of S. typhimurium are functionally related, probably by controlling the levels of the same final product (cyclic di-GMP), which include among its regulatory targets the cellulose production and biofilm formation of S. typhimurium.
243 citations
TL;DR: Analysis of a reduced model indicates that biomass redistribution, through the mechanism of swelling, may induce the formation of isolated towers or mushroom clusters by spatial variation in EPS production which leads to gradients in osmotic pressure.
Abstract: Although the initiation, development and control of biofilms has been an area of experimental investigation for more than three decades, the role of extra-cellular polymeric substance (EPS) has not been well studied. We present a mathematical description of the EPS matrix to study the development of heterogeneous biofilm morphology. In developing the model, we assume that the biofilm is a biological gel composed of EPS and water. The bacteria are enmeshed in the network and are the producers of the polymer. In response to external conditions, gels absorb or expel solvent causing swelling or contraction due to osmotic pressure gradients. The physical morphology of the biofilm depends on the temperature, solvent composition, pH and ionic concentrations through osmotic pressure. This gives a physically based mechanism for the redistribution of biomass within the biofilm. Analysis of a reduced model indicates that biomass redistribution, through the mechanism of swelling, may induce the formation of isolated towers or mushroom clusters by spatial variation in EPS production which leads to gradients in osmotic pressure.
TL;DR: Data suggest that PHA biosynthesis and alginate biosynthesis are in competition with respect to a common precursor, and indicated a functional role for PHA in stress response and tolerance.
Abstract: Pseudomonas aeruginosa is capable of synthesizing polyhydroxyalkanoic acids (PHAs) and rhamnolipids, both of which are composed of 3-hydroxydecanoic acids connected by ester bonds, as well as synthesizing the biofilm matrix polymer alginate. In order to study the influence of PHA biosynthesis on rhamnolipid and alginate biosynthesis, as well as stress tolerance and biofilm formation, isogenic knock-out mutants deficient in PHA biosynthesis were generated for P. aeruginosa PAO1 and the alginate-overproducing P. aeruginosa FRD1. A gentamicin-resistance cassette was inserted replacing the 3′ region of phaC1, the whole of phaZ and the 5′ region of phaC2. Gas chromatography/mass spectrometry analysis showed that PHA accumulation was completely abolished in both strains. Interestingly, this gene replacement did not abolish rhamnolipid production. Thus, as previously suggested, the PHA synthase is not directly involved in rhamnolipid biosynthesis. In the PHA-negative mutant of mucoid FRD1 alginate biosynthesis was not affected, whereas in the PHA-negative PAO1 mutant an almost threefold increase in biosynthesis was observed compared to the wild-type. Consistently, PHA accumulation in FRD1 contributed only 4·7 % of cell dry weight, which is fourfold less than in PAO1. These data suggest that PHA biosynthesis and alginate biosynthesis are in competition with respect to a common precursor. The surface attachment and biofilm development of the PHA-negative mutants were also compared to those of wild-type strains in glass flow-cell reactors. PHA-negative mutants of P. aeruginosa PAO1 and FRD1 showed reduced attachment to glass. However, the PAO1 PHA-negative mutant, in contrast to the wild-type, formed a stable biofilm with large, distinct and differentiated microcolonies characteristic of alginate-overproducing strains of P. aeruginosa. The stress tolerance of PHA-negative mutants with respect to elevated temperature was strongly impaired. These data indicated a functional role for PHA in stress response and tolerance.
TL;DR: The bio electric effect for Escherichia coli biofilms treated with gentamicin and with oxytetracycline is confirmed, and a new bioelectric effect with a radio frequency alternating electric current (10 MHz) instead of the usual direct current is reported.
Abstract: Bacterial biofilms are notably resistant to antibiotic prophylaxis. The concentration of antibiotic necessary to significantly reduce the number of bacteria in the biofilm matrix can be several hundred times the MIC for the same bacteria in a planktonic phase. It has been observed that the addition of a weak continuous direct electric current to the liquid surrounding the biofilm can dramatically increase the efficacy of the antibiotic. This phenomenon, known as the bioelectric effect, has only been partially elucidated, and it is not certain that the electrical parameters are optimal. We confirm here the bioelectric effect for Escherichia coli biofilms treated with gentamicin and with oxytetracycline, and we report a new bioelectric effect with a radio frequency alternating electric current (10 MHz) instead of the usual direct current. None of the proposed explanations (transport of ions within the biofilm, production of additional biocides by electrolysis, etc.) of the direct current bioelectric effect are applicable to the radio frequency bioelectric effect. We suggest that this new phenomenon may be due to a specific action of the radio frequency electromagnetic field upon the polar parts of the molecules forming the biofilm matrix.
TL;DR: It is demonstrated that the attenuation of the light intensity by the biofilm matrix represents a limitation to optical methods that is difficult to overcome in mature natural biofilms; but nevertheless, optical methods are very reliable for the study of thin or young biofilmms.
Abstract: Biofilms in surface waters are characterized by their spatial structure and the heterogeneous distribution of the microorganisms that interact in a complex and dynamic way. Therefore, the assessment of phototrophic and heterotrophic biofilms' metabolic activity should be done without disturbing their structure. Several optical methods that allow the study of undisturbed living biofilms have been developed and are claimed to have high potential in the analysis of biofilms. However, natural biofilms can develop into thick packages of cells that may limit light penetration into the biofilm matrix, hindering the use of optical methods. In this paper we evaluate the use of non-destructive optical and destructive methods for the study of natural algal-bacterial biofilms. Pulse amplitude modulation (PAM) fluorimetry (with both single and multiple wavelength excitation) and confocal laser scanning microscopy (CLSM) are used as optical methods and compared to chemical extraction of plant pigments and exopolysaccharides. We demonstrate that the attenuation of the light intensity by the biofilm matrix represents a limitation to optical methods that is difficult to overcome in mature natural biofilms; but nevertheless, optical methods are very reliable for the study of thin or young biofilms. Apart from the biofilm thickness, the degree of compactness should also be taken into account. The density of some natural biofilms could be a limitation of CLSM especially if high molecular weight probes are used for specific biofilm components. In conclusion, a combination of both approaches still appears to be necessary in order to follow the complete developmental period of biofilms. [KEYWORDS: lms ; Microalgae ; PAM fluorimetry ; CLSM ; Chlorophyll ; Lectins ; Bacteria]
TL;DR: Aerobic granular sludge was successfully cultivated in a sequencing batch reactor (SBR) treating wastewater from the malting process with a high content of particulate organic matter.
Abstract: Aerobic granular sludge was successfully cultivated in a sequencing batch reactor (SBR) treating wastewater from the malting process with a high content of particulate organic matter. At an organic loading rate of 3.2 kg/(m3 d) CODtotal and an influent particle concentration of 0.95 g/L MLSS an average removal of 50% in CODtotal and 80% in CODdissolved could be achieved. A comparison of granular and flocculent sludge grown under the same operating conditions showed no significant difference in removal efficiency although granules exhibited a higher metabolic activity in terms of specific oxygen uptake rate (rO2, X). Two distinct mechanisms of particle removal were observed for granular sludge: during initial granule formation, particles were incorporated into the biofilm matrix. For mature granules, a high level of protozoa growth on the granule surface accounted for the ability to remove particulate COD. Combined evaluation of the development in MLSS content and sludge bed settling rate (i.e., mean derivative of the normalized sludge volume) was found to be an adequate method for monitoring the characteristic settling properties of a granulizing sludge bed. By means of this method, a distinct substrate gradient out of several operating conditions was concluded to have the biggest impact on the formation of aerobic granular sludge.
TL;DR: It is shown that the matrix on C. elegans contains carbohydrate produced by Yersinia, indicating that normal animals accumulate the biofilm matrix as they move through a Yerinia lawn, while mutants with severe motility defects acquire almost no biofilm.
Abstract: Bubonic plague is transmitted by fleas whose feeding is blocked by a mass of Yersinia pestis in the digestive tract. Y. pestis and the closely related Y. pseudotuberculosis also block the feeding of Caenorhabditis elegans by forming a biofilm on the nematode head. C. elegans mutants with severe motility defects acquire almost no biofilm, indicating that normal animals accumulate the biofilm matrix as they move through a Yersinia lawn. Using the lectin wheat germ agglutinin as a probe, we show that the matrix on C. elegans contains carbohydrate produced by Yersinia. The carbohydrate is present in bacterial lawns prior to addition of nematodes, indicating that biofilm formation does not involve signaling between the two organisms. Furthermore, biofilm accumulation depends on continuous C. elegans exposure to a lawn of Yersinia bacteria.
TL;DR: To characterize the expression of coaggregation between Blastomonas natatoria 2.1 and Micrococcus luteus following growth in liquid culture, on agar and in an artificial biofilm matrix composed of poloxamer hydrogel.
Abstract: A . H . R I C K A R D , P . G I L B E R T A N D P . S . H A N D L E Y . 2004. Aim: To characterize the expression of coaggregation between Blastomonas natatoria 2.1 and Micrococcus luteus 2AE13 following growth in liquid culture, on agar and in an artificial biofilm matrix composed of poloxamer hydrogel. Methods and Results: The ability of B. natatoria 2AE1 and M. luteus 2AE13 to coaggregate with one another was assessed following growth in liquid culture as colonies on agar or within a poloxamer hydrogel matrix. In all these environments a cycle of gain and loss of coaggregation occurred when the two cell types were aged simultaneously, with optimum expression occurring in early stationary phase. Blastomonas natatoria 2AE1 cells only coaggregated maximally after entry into stationary phase. Conversely, M. luteus 2AE13 cells only coaggregated in exponential phase and early stationary phase and coaggregation ability was lost in late stationary phase. Maximal coaggregation therefore only occurred between the two strains if both were in early stationary phase, when the surface properties of the two cell types were optimal for coaggregation. Conclusion: In addition to occurring between cells grown in liquid culture, coaggregation between aquatic bacteria occurs after growth as a biofilm on agar and in an artificial biofilm matrix in poloxamer. Under all conditions, the B. natatoria 2AE1 coaggregation adhesin and complementary receptor on M. luteus 2AE13 were only expressed simultaneously during early stationary phase.
TL;DR: It was demonstrated that in several polymers (alginate, dextran, levan and others) a typical extracellular enzyme, the alpha-amylase, develops enhanced resistance against desiccation stress.
Abstract: Microbial biofilms are ubiquitous in aquatic and terrestric ecosystems as well as on man-made material. They are initial colonizers on all surfaces and take part in biogenic weathering on natural rocks as well as on building stone. The structure and function of the biofilm matrix, mainly extracellular polysaccharides (EP), is documented for biofilms on stone surfaces: the hydrated gel acts as glue between the organisms and the material surface. Besides EP, living cells, cell debris and mineral particles are embedded in the matrix. These particles appear to be deposited on the surfaces of cell walls and interfaces in the biofilm matrix. As an important function of the matrix, EP stabilizes the biological activity against periodic desiccation. It was demonstrated that in several polymers (alginate, dextran, levan and others) a typical extracellular enzyme, the alpha-amylase, develops enhanced resistance against desiccation stress. Consequences of EP production and biofilm development on surfaces are discussed.
TL;DR: Findings could be the higher microbial diversity, higher metabolic activity of attached bacteria and abiotic adsorption of organic molecules to inorganic support and biofilm matrix surfaces, which is easily hydrolyzed and utilized by biofilm bacteria.
TL;DR: In this paper, photoacoustic spectroscopy (PAS) was employed for biofilm monitoring, which allowed the depth-resolved investigation of growth and detachment processes of biofilms.
TL;DR: Individual-based modelling of biofilms structure dynamics is used here to unify observations from the operation of biofilm reactors by simulating biofilm growth under variable detachment forces and mass transport regimens for a growth-limiting substrate.
Abstract: In spite of the large range of morphologies observed for biofilms, there is strong experimental and theoretical evidence that the complex nature of biofilm structure dynamics is primarily a consequence of the effect of environmental conditions on biofilm development. It has been observed from the operation of industrial and laboratory-scale biofilm reactors that the structure of biofilms results from a balance of the detachment forces and the regimen of transport of a growth-limiting substrate. The overall performance of biofilm reactors is intrinsically dependent on biofilm morphology. The spatial distribution of the diverse dissolved and particulate components through the biofilm matrix and the shape of its external surface influence the rates of the occurring bioconversions, and structure also influences the stability of the biofilm in terms of resistance to mechanical stress. Individual-based modelling (IbM) of biofilms structure dynamics is used here to unify observations from the operation of biofilm reactors by simulating biofilm growth under variable detachment forces and mass transport regimens for a growth-limiting substrate. The IbM is a bottom-up approach, where the global system behaviour is derived from the local interactions of multiple elements acting independently. Transport and reaction of a solute species, local microbial growth rates and the effect of external detachment forces applied to the biofilm are modelled using differential approaches. Simulations carried out in two-dimensional space using this model illustrate a range of biofilm morphologies that emerge from different reactor operation parameters, reproducing trends observed experimentally. Comparison of multi-dimensional modelling results with those obtained using one-dimensional approaches enforces the need to use multidimensional modelling to predict properties that derive from the spatial biofilm structure.
TL;DR: In this article, a dual-species biofilm barrier is proposed to not only control contaminant migration through permeability reduction, but also facilitate contaminant biodegradation by using a biofilm matrix.
Abstract: Biologically produced subsurface barriers (i.e., biofilm barriers) are a viable technology for controlling contaminant migration from hazardous waste sites. Biofilm barriers are created through the injection of bacteria and selective growth medium into a series of wells downstream of a contaminant plume. Adequate substrate addition enables the bacteria to grow and form thick biofilms capable of uniform plugging of the subsurface. This technology has been successful in significantly reducing porous media permeability in bench-scale and field-scale applications. The research presented herein expands on current biofilm barrier technology by examining the feasibility of using a biofilm barrier to not only control contaminant migration through permeability reduction, but also facilitate contaminant biodegradation. The experimental scenario involved the creation of a dual-species biofilm matrix: one organism to reduce porous media permeability through thick biofilm formation and another organism to degrade a contaminant, in this case trichloroethylene (TCE). Porous medium column experiments demonstrated that a dual-species biofilm barrier can be created and that growth medium concentration was a very important variable in controlling simultaneous TCE degradation and permeability reduction. © 2004 American Institute of Chemical Engineers Environ Prog, 23: 69–77, 2004
01 Jan 2004
TL;DR: It has been reported that Candida albicans biofilms are up to 4,000 times more resistant to fluconazole compared with planktonic, free-floating cells.
Abstract: Biofilms are a primitive type of developmental biology in which spatial organization of the cells within the matrix optimizes the utilization of the nutritional resources available; they incorporate an immobilized enzyme system in which the millieu and the enzyme activities are constantly changing and evolving to the appropriate steady state. The biomaterial properties affecting initial adhesion range from chemical properties to hydrophobicity to surface roughness. Since these biomedical devices are usually surrounded by body fluids, such as urine, blood, saliva, and synovial fluid, their surfaces often acquire a glycoproteinaceous conditioning film following implantation. For short-term urinary catheterization, up to 50% of the patients develop an associated urinary tract infection (UTI), but almost all patients undergoing long-term catheterization ultimately became infected with associated device colonization organisms. Several groups have demonstrated that the Candida biofilm lifestyle leads to dramatically increased levels of resistance to the most commonly used antifungal agents, fluconazole and amphotericin B. Different mechanisms may be responsible for the intrinsic resistance of Candida biofilms. These include: (i) effects of the biofilm matrix on penetration of drugs, (ii) decreased growth rate and nutrient limitation, (iii) expression of resistance genes, particularly those encoding efflux pumps, and (iv) presence of “persister” cells. It has been reported that Candida albicans biofilms are up to 4,000 times more resistant to fluconazole compared with planktonic, free-floating cells.
TL;DR: The removal of a common azo dye, acid orange 7 (AO7), in biofilm systems was investigated and the adsorption of AO7 onto biofilm matrix and activated sludge flocs was found to fit the Langmuir equation, however, there is a significant difference in the advertisersorption capacities between biofilm andactivated sludge.
Journal Article•
TL;DR: ICX is effective in maintaining the effluent within the American Dental Association's and the Centers for Disease Control's recommendation for < 500 CFU/ml and may be useful in long-term treatment alone or when coupled with a shock treatment to assist in biofilm destruction.
Abstract: OBJECTIVE Even though some chemical agents can disinfect biofilms in dental unit waterlines, there remains concern that all remnants of the biofilm matrix are not eliminated. Even with periodic treatments, the bacterial populations in dental unit waterlines recur rapidly. In addition, with some previously tested products, patient safety, as well as toxic, caustic and corrosive residual chemicals are also a concern. This study evaluated ICX, A-dec's new water treatment solution, in a series of experiments for prevention, microbial spectrum of activity, minimum inhibitory time determination, and treatment of established biofilms. METHODOLOGY New dental unit waterline tubing was treated continuously during simulated patient care over 28 days with municipal water. It was then treated with ICX. Effluents from lines with established biofilms (averaging > 10(4) CFU/ml at day 0) were treated to assess levels of CFU counts within 21 days of exposure to ICX. RESULTS Tubing treated with ICX did not develop a detectable biofilm using ruthenium red staining, and microbes in effluents remained undetectable. CONCLUSION ICX is effective in maintaining the effluent within the American Dental Association's and the Centers for Disease Control's recommendation for < 500 CFU/ml. In addition, considering the preliminary finding that ICX reduces microbial contamination of effluents from established biofilm lines, it may be useful in long-term treatment alone or when coupled with a shock treatment to assist in biofilm destruction.
TL;DR: 3-D images revealed the 3-D distribution of specific biofilm components such as filaments of sheathed bacteria projecting outward into the liquid milieu, and organic coatings, including bacterial cells on the surfaces of mineral particles in the mature biofilms.
Abstract: Aufwuchs chamber slides were constructed by attaching a silicone rubber gasket to a glass slide with epoxy cement. For biofilm growth, the slides were suspended in Cayuga Lake near Ithaca, NY, for 27 days. Biofilms in the chamber were stained with 0.05% acridine orange. After rinsing, the chamber was filled with molten 1% agarose to stabilize filaments and delicate polymer structures at the biofilm surface. Areas of biofilm ~0.5 mm thick on the inner face of the wall of the chamber were selected for side-on optical sectioning in a confocal laser scanning microscope (CLSM). Stacks of high-resolution optical images captured by the CLSM z-sectioning software, were used to create left-right stereo image pairs. At low magnification the stereo pairs showed 3-D details of the microbial landscape in the mature biofilms. Channels, pores, and other structural features of the biofilm matrix were observed in peripheral regions. Higher magnification images revealed the 3-D distribution of specific biofilm components such as filaments of sheathed bacteria projecting outward into the liquid milieu, and organic coatings, including bacterial cells on the surfaces of mineral particles.